1. Field of the Invention
The present invention pertains to vehicle wheel drive systems, and more particularly, it pertains to steerable power-driven wheels.
2. Description of the Prior Art
Relatively light high mobility tactical motor vehicles are quite useful in moving people and supplies over relatively rugged terrain where commercial automobiles and trucks are not able to travel. These tactical vehicles are especially useful in transporting military personnel, sportsmen, hunters and supplies into areas which are off the normal roads and highways. To reduce the chances of the vehicle becoming stuck in sand, mud or loose dirt and to enable the vehicle to carry larger payloads over the rugged terrain it is desirable that power be applied to all of the wheels of such a vehicle.
It is important that these off-the-road vehicles have a relatively high ground clearance and that the axles be raised to provide protection from damage and allow the vehicles to move freely over rocks, stumps and other obstacles. It is also essential, of course, that wheels on at least one end of the vehicle be steerable.
Some widely used vehicles, including the Volkswagen Microbus, mount a final-drive gear-reduction unit directly upon the wheels which are to be powered. However, these vehicles have the in-the-wheel gearing unit mounted on the rear wheels which are not steerable. The gear-reduction unit serves to convert a high-speed low-torque input into a lower-speed higher-torque output. This allows the use of a relatively small drive shaft between the motor and the differential gears and relatively small drive axles between the differential gears and the gear-reduction units at the drive wheels. Each in-the-wheel gear-reduction unit is mounted with the drive axle above the wheel axle to provide greater ground clearance for the drive axle which is coupled between the gear-reduction unit and the differential gears to provide power to the wheels.
One type of prior art apparatus having a steerable wheel with a gear-reduction unit at the wheel is shown in the prior U.S. Pat. No. 2,762,632 to Irvin. This apparatus includes a relatively complex suspension system which concentrates the wheel-related loads at the very front end of the vehicle and which generally comprises a pair of arms, a pair of torsion bars and a spring to connect each of the wheels to the frame of the vehicle.